modern eyes
When we want to get a look at something we are usually most
prepared to do literally that; take a glance with our eyes.
Eyes generally do not provide a permanent image for us to work
with, though, and is rather limited to a small band of light -
the visible spectrum of electromagnetic radiation. Likewise,
the size, distance, or make-up of an object can prevent our
eyes from being a useful tool. Instead, we have cameras,
telescopes, and other sensor devices that we can use to
translate the world around us into something our eyes (and
heads) can make sense of.
Satellite mounted cameras are an important tool for looking
at and studying many things that would be difficult or
impossible from the ground. They let us investigate and image
on a scale and in finer detail than would otherwise be
possible. They are not without their own limitations. Our eyes
can perceive the visible spectrum, all of it, at varying
levels of sensitivity. Our instrument can sense a much wider
selection of wavelengths on the EM spectrum but with a caveat;
the sensors are generally restricted to specific wavelengths.
By working with and around these quirks, we can create visible
images representing a range of data. The information that a
satellite sensor can 'see' is often reliant on a few important
facets of how EM waves interact with things -
reflection, absorption and transmission.